Question

A 75-kilogram hockey player is skating across the

Answer 1

I think it is (3) 690 N. You can use the theorem of Impulse and momentum where the impulse is equal to the change in momentum or:
$F \Delta t=m v_{f}-m v_{i}$ (where f is for final and i for initial).
So you get:
$F*0.65=0-(75*6)$
$F=692 N$